DE69112712T2 - Detergent composition. - Google Patents

Description

Field of the invention

This invention relates to a detergent composition. More particularly, it relates to a detergent composition which is suitable for washing the body, hair and skin and which is convenient to use.

Description of the current state of the art

Personal care detergent compositions usually contain the well-known anionic surfactants. Soaps, i.e. the salts of higher fatty acids, are used mainly for cleaning the skin, while alkyl sulfates or alkyl sulfonates are used mainly for washing the hair.

The soaps used to clean the skin have the disadvantage that the soap scum formed during rinsing - the calcium salts of higher fatty acids - adhere to the skin, which greatly impairs the lubricity of the skin surface and causes a feeling of roughness or tension. To avoid this disadvantage, attempts have been made to develop compound types of cleaning agents by adding an oily component such as a higher alcohol or a humectant such as propylene glycol to the aforementioned soaps or by using an anionic surfactant which never forms any kind of soap.

However, the addition of small amounts of such an oily component may not achieve the desired effect. On the other hand, the addition of a large amount of an oily component may cause another problem that the foaming properties are significantly deteriorated. If such an anionic surfactant, which does not If a detergent that forms lime soap is used, the roughness decreases when the amount of the surfactant is increased. However, if it is used in such an amount that a sufficient effect is achieved, then the foam-suppressing effect is delayed and the detergent composition becomes slimy.

On the other hand, the alkyl sulfates and alkyl sulfonates mentioned above, used for washing hair, do not form lime soaps and therefore never cause the same feeling of roughness or tension as is observed when using soap. However, a detergent composition made from these components has poor foam-suppressing properties and cannot provide the hair with lubricity. To avoid these disadvantages, attempts have been made to add oily components such as higher alcohols, carbonic acids or silicones. In this case, however, the addition of these oily components in small quantities cannot achieve the desired effect and the addition of large quantities would significantly impair the foam-forming properties of the detergent composition.

Surfactants containing N-alkyl-N-acyl-amino acids are known. For example, JP-A-150701/1975, JP-A-2962/1988, JP-A-60 139612 and JP-A-59 207 944 each disclose a liquid detergent composition containing as a surfactant an N-alkyl-N-acyl-amino acid having a long-chain acyl group, which is a less skin-irritating surfactant than a base. In addition, JP-A-132007/1978 discloses an improved solid detergent composition containing a neutral N-acyl-amino acid having a long-chain acyl group.

Although the salts of N-alkyl-N-acyl-amino acids, which have a tertiary amide structure and are described in these citations and used as cleaning compositions, are highly soluble in water, they have poor foam-suppressing properties and offer little comfort during use, since they are somewhat greasy.

The compositions disclosed in Japanese patent applications JP-A-2962/1988 and JP-A-1178597 also contain the sodium salt of N-lauryl-β-alanine, which has a secondary amide structure (see Example 5 therein). However, this compound is poorly soluble in water, which makes it unsuitable for use in a liquid detergent composition. The addition of a 1% solution of this compound, as indicated in Table 1 of the cited reference, also cannot provide the desired convenience in use.

Summary of the invention

It is an object of the present invention to provide a cleaning composition which is very easily soluble in water, has good foaming properties during cleaning, but does not foam quickly during rinsing, does not become greasy, gives the surface of the material to be cleaned a high level of slip from the rinsing process until after drying, is less irritating to the skin, does not cause a feeling of roughness or tension after the end of the application and offers excellent comfort during its application.

The present inventors have conducted extensive investigations and found that the above-mentioned objects can be achieved by using specific N-acyl compounds as the main component of the detergent composition.

Accordingly, the present invention, which has been completed on the basis of the above-mentioned finding, provides a liquid detergent composition containing 5 to 60% by weight of a potassium salt of an N-acyl amino acid having a secondary amide structure represented by the following general formula (I)

RCONHCH₂CH₂COOH (I) wherein RCO represents an acyl group having a straight-chain, saturated hydrocarbon radical having 10 to 14 carbon atoms.

Each of the liquid detergent compositions of the present invention is readily soluble in water, has good foaming properties during cleaning, but quickly stops foaming during rinsing, does not become greasy, provides high lubricity to the surface of the material to be cleaned from the rinsing process to after drying, is less irritating to the skin, causes neither a feeling of roughness nor tightness after the end of use, and offers excellent comfort during use. Therefore, this detergent composition is particularly suitable for skin cleansing (body and face) and for washing hair.

Detailed description of the invention

The potassium salt of N-acyl amino acid, represented by the above general formula (I) and hereinafter also referred to as N-acyl compound, which is one of the components of the cleaning composition, reacts with calcium salts contained in tap water to form plate-shaped crystals which are good lubricants.

The RCO group in the above general formula (I) of the aforementioned N-acyl compound is an acyl group having a straight-chain saturated hydrocarbon residue of 10 to 14 carbon atoms, particularly a lauroyl group having 12 carbon atoms. In this case, if the number of carbon atoms exceeds 14, the lubricity of the plate-shaped crystals formed and the foaming properties of the detergent composition are deteriorated. On the other hand, if the number of carbon atoms is less than 10, the foaming properties are deteriorated. Therefore, these two cases are not desirable.

The lubricity of the plate-shaped crystals formed by the reaction of the above-mentioned N-acyl compound with calcium salts can be determined, for example, by measuring the static friction coefficient of the plate-shaped crystals on dried pigskin (ALLOASK, a product of Kotai Kasei Kogyo K.K.) that has been reconstituted with a physiological saline solution. That is, plate-shaped crystals with a static friction coefficient that was lower than that of a blank sample during the influence of moisture until after drying was completed are classified as good.

It is very important that the above-mentioned N-acyl compound has a secondary amide structure, the N-acyl group being composed of the straight-chain acyl residue mentioned above. If the acyl group forming the N-acyl group is branched or the amide has a tertiary amide structure, the formation of the plate-shaped crystals is suppressed or the crystals formed have poor lubricity and are therefore sticky. In these cases, therefore, a desired surface texture can hardly be obtained.

The above-mentioned N-acyl compound is a potassium salt (hereinafter sometimes referred to as K) of an N-acyl amino acid represented by the above general formula (I). It is not convenient to use a sodium salt (hereinafter sometimes referred to as Na) of an N-acyl amino acid because it has a high Krafft point and a low water solubility and is therefore unsuitable for a liquid detergent composition.

The content of the above-mentioned N-acyl compound may be in the range of 5 to 60 wt.%, preferably in the range of 20 to 50 wt.%, based on the liquid detergent composition.

If this content is less than 5% by weight, the feeling of refreshment and comfort resulting from the formation of plate-shaped crystals during the rinsing process cannot be achieved during use. On the other hand, if this content is 60 % by weight, the liquid detergent composition forms a gel and therefore a good liquid detergent composition cannot be obtained.

The above-mentioned N-acyl compound (a salt of an N-acyl amino acid with a secondary amide structure) can be prepared, for example, by the following process. An amino acid is acylated using the well-known Schotten-Baumann reaction, in which an aqueous alkaline solution of the amino acid and sodium hydroxide are reacted with the acid chloride of a fatty acid.

The reaction mixture is then acidified with hydrochloric acid to obtain the N-acyl amino acid (as a free amino acid). The product is filtered off, dried and then neutralized with potassium hydroxide. In this way, the N-acyl amino acid with a secondary amide structure can be obtained.

If necessary, the liquid cleaning composition can be made into a paste or gel by adding a thickener or a binder.

The liquid detergent composition may also contain ingredients that are usually used in detergent compositions, such as humectants, touch improvers, viscosity modifiers, bactericides, perfumes or dyes, as long as they do not prevent the formation of the plate-shaped crystals that serve as good lubricants during the rinsing process.

The pH of the liquid detergent composition may be greater than or equal to 6, and is preferably in the range of 7 to 10.

The liquid cleaning composition described in detail above is suitable for cleaning the body, skin and hair. It is particularly suitable for cleaning the skin.

To further illustrate the present invention, but not to limit it, the following examples are given.

example 1

Each liquid detergent composition of the formulation given in Table 1 was prepared and its solubility, foaming properties, precipitation of plate-shaped crystals and comfort of use were evaluated in accordance with the criteria given below. The results are summarized in Table 1.

Assessment of solubility

The appearance of each liquid detergent composition at 10ºC was evaluated with the naked eye in accordance with the following criteria.

Criteria:

o : transparent

x : cloudiness or appearance of a precipitate due to the formation of crystals

Evaluation of foaming properties

The foam volume was determined by the following method and the foaming properties were thus evaluated in accordance with the criteria given below. Each liquid detergent composition was diluted tenfold with water. 100 ml of the aqueous solution thus obtained was poured into a graduated cylinder at 20ºC (temperature measurement in the liquid). Then, the agitator blades were immersed in the solution and the foam volume (ml) formed within 30 seconds after the start of agitation was measured. The value thus determined was defined as the foam volume. The agitator blades rotated at 1000 revolutions per minute and the direction of rotation was reversed every 5 seconds.

Criteria:

: The foam volume is greater than 200 ml

o : The foam volume is in the range of 150 to 200 ml

x : The foam volume is less than 150 ml

Evaluation of the formation of a precipitate of plate-shaped crystals that serve as lubricants.

Each liquid detergent composition was diluted tenfold with ion-exchanged water. 1 ml of the thus-obtained aqueous solution was poured into 50 ml of water (hardness: 4ºDH; temperature: 20ºC). After 10 seconds, the formation of crystals was evaluated with the naked eye and in accordance with the criteria mentioned below.

Criteria:

: Crystal formation and turbidity of the ibsung

: Crystal formation and slight turbidity of the solution

x : No crystal formation and the solution remains transparent

Assessment of comfort during use

Ten male and ten female panelists washed their bodies with each liquid detergent composition for one week, and the comfort of using each product was organoleptically evaluated. The results shown in Table 1 in accordance with the criteria below were the average values from the test data.

Criteria: (1) Anti-foaming properties during rinsing:

5: Very good

4: Good

3: Mediocre

2: Bad

1: Very bad

(2) slippage during rinsing;

(3) lubricity after rinsing; and

(4) Slip after drying:

5: Very good

4: Good

3: Mediocre

2: Bad

1: Very bad Table 1 (Formulation: % by weight) Invention Comparative examples N-lauroyl-β-alanine (salt) N-stearoyl-β-alanine (K salt) N-lauroyl-N-methyl-β-alanine (Na salt) Purified water Solubility evaluation Foaming evaluation Comfort of use Foam suppression during rinsing Slip during rinsing Slip after rinsing Slip after drying

Note: An * means that no liquid cleaning agent composition could be obtained due to crystal formation at room temperature and therefore an evaluation was impossible. A b means "the remainder".

Example 2

For the potassium salts of N-acyl amino acids with secondary amide structure used in liquid detergent compositions, the solubility, the formation of slippery plate-shaped crystals and the ease of use were evaluated in accordance with the criteria given below. For comparison, the sodium salts of N-acyl amino acids with secondary amide structure and the salts of N-alkyl-N-acyl amino acids with tertiary amide structure were evaluated in the same way. The results and the Krafft points of these salts of amino acids are shown in Table 2.

Assessment of solubility

A 5% (wt%) aqueous solution of a salt of each amino acid was prepared and the solubility of the salt at 10ºC was evaluated in accordance with the criteria given below.

Criteria:

o : Soluble

x : Insoluble (precipitation of crystals)

Evaluation of the formation of slippery, plate-shaped crystals

A 5% (wt.%) aqueous solution of a salt of each amino acid was prepared and 1 ml of the resulting solution was poured into 50 ml of water (hardness: 4ºDH; temperature: 20ºC). After 10 seconds, the formation of crystals was determined and evaluated in accordance with the criteria given below.

Criteria:

0 : Formation of crystals

x : No formation of crystals

Assessment of comfort during use

A 5% (wt%) aqueous solution of a salt of each amino acid was prepared and a subject washed his body with the resulting solution. Then the slippage was measured from the Rinsing and drying in accordance with the criteria set out below.

Criteria:

: Very good

0 : Good

x : Bad Table 2 Krafft point Solubility Crystal structure Ease of use Caprinoyl-β-alanine Lauroyl-β-alanine Myristoyl-β-alanine Lauroyl-N-methyl-β-alanine Salt Example 3 (Formulation) (wt.%) N-Lauroyl-β-alanine (potassium salt) Dibutylhydroxytoluene Perfume Ethanol Purified water Rest

In accordance with the above recipe, component (1) was dissolved in hot water. After cooling, components (2) to (4) were added. In this way, a transparent, liquid cleaning composition was prepared.

When the skin and hair were washed with the liquid detergent composition obtained above, the product showed good foaming properties, good anti-sudsing properties, good slip from the rinsing process to the drying process and excellent comfort during application.

Claims (2)

1. A liquid detergent composition containing 5 to 60% by weight of a potassium salt of an N-acyl amino acid having a secondary amide structure represented by the following general formula (I): RCONHCH₂CH₂COOH (I) wherein RCO represents an acyl group having a straight-chain, saturated hydrocarbon radical with 10 to 14 carbon atoms. 2. A liquid detergent composition according to claim 1, wherein RCO in the general formula (I) is a lauroyl group.